Instrumented antifriction bearing and electrical motor equipped therewith

ABSTRACT

An instrumented ball-bearing includes a rotating part, a non-rotating part, and an assembly for detecting rotation parameters. The assembly for detecting rotation parameters includes an encoder and a sensor. The sensor is integrated with the non-rotating part. The sensor includes a sensor unit and at least a microcoil. The microcoil has a substantially planar winding. The microcoil is positioned in the sensor unit of the non-rotating part such that the microcoil is positioned axially opposite the encoder.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to an antifriction bearing inwhich a rotating member of the bearing supports an encoder and anonrotating member of the bearing supports a sensor that may be used todetermine rotation parameters such as the speed or the angular positionof the rotating element supporting the encoder. The present inventionalso relates to antifriction bearings for use in electric motors, whichare required to operate in severe speed and temperature conditions.

2. Description of the Relevant Art

French Patent No. 2,754,903, describes an antifriction bearing thatincludes a sensor on the nonrotating track, of the Hall effect probetype, and an encoder on the rotating track moving in rotation with aslight air gap relative to the sensor while being capable of producingin the sensor a periodic signal with a frequency proportional to therotation speed of rotation of the rotating track. The encoder includesan annular active portion. The annular active portion includes a plasticmagnet and an active portion placed opposite the sensor. The activeportion may be supplemented by a reinforcement portion that includes twoannular elements placed in contact with the active portion on eitherside of the active zone.

This type of antifriction bearing is usually satisfactory, particularlyin the field of electric motors. However, this type of encoder cannotoperate at temperatures above 120°. In addition, the sensor and theencoder do not operate satisfactorily if they are subjected to highintensity external magnetic fields, for example the magnetic fieldsinduced by the coils of the stator of electric motors and/or by theelectromagnetic brake built into the motors. Finally, the axialcompactness of this type of antifriction bearing is not optimal and isnot easy to incorporate.

In high power asynchronous electric motors, control of the motorrequires detection of the rotation parameters of the motor. Knowledge ofspeed and direction of rotation of the rotor may be needed to adapt thefrequency and the direction of the current entering the coils of thestator. The use of a multipolar type encoder associated with a Halleffect probe is suitable only for applications in which the power andthe control requirements are relatively imprecise, for example for a fanmotor that operates at constant speed during use. Optical type sensorencoder systems, such as industrial encoders, require a mechanicalinterface for driving by the electric motor and are relatively sensitiveto impacts and to temperature. Optical type sensor encoder systems arenot likely to be built into a motor.

The invention aims to remedy these disadvantages.

SUMMARY

Herein we describe an instrumented antifriction bearing that may beaxially compact and may operate at high temperatures while deliveringprecise detection. The antifriction bearing may also including when theyare subjected to intense magnetic fields.

In some embodiments, the instrumented antifriction bearing device mayinclude a rotating portion, a nonrotating portion and an assembly fordetecting rotation parameters. An assembly for detecting rotationparameters may include an encoder and a sensor. A sensor may beintegrated with the nonrotating portion and may include a sensor unit. Asensor may include at least one microcoil with a substantially flatwinding. A microcoil may be positioned on a support of a circuit mountedin the sensor unit of the nonrotating portion so that the microcoil maybe axially opposite the encoder. This may provide satisfactory axialcompactness.

In one embodiment, the device may include a plurality of substantiallyradial coplanar reception microcoils, which may allow substantiallyprecise detection. In certain embodiments, the device may include aplurality of reception microcoils positioned on a plurality of parallelradial planes. An increased number of reception coils may provideenhanced precision.

In some embodiments, the device may include a transmission coilpositioned in the sensor unit. The transmission coil may also be amicrocoil. A microcoil may have a flat winding. In an embodiment, adevice may include at least one transmission coil, at least onereception coil, and a data processing circuit positioned on the support.These elements may be used to retain a desired axial compactness. Thecoils may be made using printed circuit technology. The support mayinclude a printed circuit substrate in the form of a resin circuitboard. A sensor may include active and/or passive elements combined in asingle module integrated with the nonrotating portion.

In some embodiments, the device may include a plurality of microcoils.Microcoils may be coupled in pairs and/or angularly offset in order togenerate a differential signal. The encoder may include an encoderwheel. An encoder wheel may include an active zone made of anelectrically conducting metal. In certain embodiments, the encoder mayinclude a printed circuit with an annular shaped substrate that includesmetallized sectors and nonmetallized sectors. The printed circuit may bemounted on a nonrotating track of the antifriction bearing.

In some embodiments, the encoder may include an encoder wheel withwindows and/or teeth attached to a rotating track of the antifrictionbearing. The encoder may be a substantially solid block. The encoder maybe pressed sheet metal. An encoder may operate at high temperatures. Forthe purposes of this application, windows refer to holes formed in theencoder between two circumferentially continuous portions. For thepurposes of this application, teeth refer to portions of material thatare integrated with a circumferentially continuous portion of theencoder. The encoder may include an axial portion positioned on acylindrical bearing surface of the rotating track and a radial portiondirected towards the other track and in which the windows or the teethare formed.

To increase compactness, at least one portion of the encoder may bepositioned in the space situated between the antifriction bearingtracks. For example, a portion of the encoder may be positioned radiallybetween the cylindrical surfaces of the tracks which extend between thebearing raceways and the frontal surfaces delimiting said tracks andaxially, at right angles to the cylindrical surfaces, between therolling elements and the frontal radial surfaces of the antifrictionbearing tracks. In certain embodiments, the encoder may be positionedoutside the space situated between the antifriction bearing tracks.

In some embodiments, the sensor unit may be annular. In anotherembodiment, the sensor unit may occupies an angular sector of less than360°, for example approximately 120°. In certain embodiments, the dataprocessing circuit may be an application-specific integrated circuit(ASIC).

In some embodiments, an electric motor may include a rotor, a stator, atleast one antifriction bearing supporting the rotor, and a sensorassembly including an encoder and a sensor. The sensor may include atleast one microcoil with a substantially flat winding positioned on asupport of a circuit that is mounted in the sensor unit and integratedwith the stator such that the microcoil is positioned axially oppositethe encoder. In an embodiment, a winding may include an outer trackintegral with the stator and supporting the sensor unit and an innerrotating track integral with the rotor and supporting the encoder. Themotor may be of the high power asynchronous type in which precisecontrol may be required and facilitated by measuring the rotationparameters precisely. For the purposes of this application, a microcoilrefers to a coil with a winding formed on a circuit. For example, amicrocoil may include a copper coil on a printed circuit substrate. Thethickness of the card and the microcoil may be approximately 1 mm.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the methods and apparatus of the presentinvention will be more fully appreciated by reference to the followingdetailed description of presently preferred but nonetheless illustrativeembodiments in accordance with the present invention when taken inconjunction with the accompanying drawings in which:

FIG. 1 depicts a view of an axial section of an embodiment of aninstrumented antifriction bearing;

FIG. 2 depicts a partial view of the sensor of FIG. 1;

FIG. 3 depicts a frontal view in elevation of the encoder of FIG. 1;

FIG. 4 depicts a frontal view in elevation of an embodiment of anencoder variant;

FIG. 5 depicts a view of an axial section of an embodiment of aninstrumented antifriction bearing;

FIG. 6 depicts a frontal view in elevation of the encoder of FIG. 5; and

FIG. 7 depicts a wiring diagram of an embodiment of a sensor.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and will herein be described in detail. Itshould be understood, however, that the drawings and detaileddescription thereto are not intended to limit the invention to theparticular form disclosed, but on the contrary, the intention is tocover all modifications, equivalents and alternatives falling within thespirit and scope of the present invention as defined by the appendedclaims.

DETAILED DESCRIPTION OF EMBODIMENTS

As illustrated in FIG. 1, the rolling bearing 1 may include an outertrack 2; an inner track 3; a row of rolling elements 4, such as balls,placed between the outer track 2 and the inner track 3 and retained by acage 5; a seal 6 on one of its sides; on the opposite side a speedsensor 5 integrated with the outer track 2; and an encoder 8 integratedwith the inner track 3. In an embodiment, the outer track may benonrotating and the inner track may be rotating. In an embodiment, theouter track may be rotating and the inner track may be rotating.

In some embodiments, a sensor 7 may include a detection portion 9 asdepicted in greater detail in FIG. 2. A sensor may include a supportunit 10 made of a synthetic material and a metal element 11 fitted ontoa bearing surface of the outer track 2. A groove in a track may be usedto attach the seal provided in noninstrumented antifriction bearings. Acable 12 may be coupled to the detection portion 9 and may be used totransmit information about speed, position, and/or or rotationparameters. Information may be transmitted to any unit that are capableof exploiting the data.

In some embodiments, an encoder 8, as depicted in FIGS. 1 and 3, mayinclude a support portion 13 and an operational portion 14. The supportportion 13 may tubular in shape. The support portion 13 may bepositioned on a cylindrical bearing surface 3 a of the inner track 3formed between the trackway 3 b which is coupled with the rollingelements 4 and a radial surface 3 c which forms the end of the innertrack 3 in the axial direction on the side of the sensor. Theoperational portion 14 may be radial and may include a plurality ofwindows 15. Windows may have a rectangular shape and may be elongatedradially at the large diameter end of the operational portion 14,allowing a continuous circular portion 16 to remain. The operationalportion 14 and the support portion 13 may be a solid unit and mayprovide an economic and particularly robust construction. The encoder 8may be a metal sheet formed by means of pressing and punching steps. Theoperational portion 14 may be slightly recessed relative to the radialsurface 3 c of the inner track 3. The encoder 8 may be particularlycompact and positioned in the space defined radially between the tracks2 and 3 of the rolling bearing and axially between the rolling elements4 and the radial plane through which the end surfaces 2 c, 3 c of saidtracks 2 and 3 pass.

In some embodiments, a detection portion 9 of the sensor 7 may include asupport 17, a transmission microcoil 19, and at least four receptionmicrocoils 20. An integrated circuit 18, such as an ASIC type, may bemounted on a support 17 and may be used to process data. A transmissionmicrocoil 19 may include an excitation coil. The circuit may include apredetermined number of filtering elements such as capacitors,resistors, etc., which are not shown. The detection portion 9 may bepositioned axially at a slight distance from the operational portion 14of the encoder 8 and may occupy an angular sector of approximately 120°while being inserted into the support unit 10, which may besubstantially circular. In an embodiment, a continuous angular sector of360° may be provided for insertion of the detection portion into thesupport unit. The detection portion 9 may include a face, orientedfacing the encoder 8, that is not substantially covered by the materialof the support unit 10.

In some embodiments, microcoils 19 and 20 may be flat winding types ofmicrocoils. Microcoils may be printed circuits or integrated circuits.The flatness of the windings may provide the sensor 7 with excellentaxial compactness. In addition, the reception coils 20 may have a squareouter contour. Reception coils may be positioned one after the other onthe arc of a circle formed by the support 17, while the transmissioncoil 19 substantially surrounds the reception coils 20 and is shapedlike an arc of a circle. The coils 19 and 20 may be coupled to the dataprocessing circuit 18. The coils 19 and 20 may be coupled to the cable12.

A metal element 11 may include a portion that forms a hook 11 a bentinto a groove of the outer track 2 that may be used for fastening asealing element which, in a noninstrumented antifriction bearing, may besubstantially symmetrical with the seal 6. The metal element 11 may besupplemented by a short radial portion directed outward from the portion11 a and an axial portion 11 c extending from the free end of the radialportion 11 b. A short radial portion may be in contact on one side withthe end radial surface 2 c of the outer track 2 and on the other sidewith the support unit 10 of the sensor 7. An axial portion 11 c mayradially surround the support unit 10, with the exception of the cableoutlet zone 12 where the support unit 10 may extend outward forming aprotuberance 21 surrounding the cable 12 and protecting its outlet.

In some embodiments, a support unit 10 may be made of a syntheticmaterial and may have a generally annular shape with the protuberance 21projecting over its periphery. A support unit may have an axial hollowon its radial face on the side of the antifriction bearing thatconstitutes a housing for the detection portion 9 while covering thedetection portion on its face opposite the rolling bearing and over itsthickness in the radial direction. The support unit 10 and the detectionportion 9 may be integrated. In one embodiment, the support unit 10could be metallic.

FIG. 4 depicts an embodiment of an encoder in which the support portion13 is similar to FIG. 3. The operational portion 14 may be orientedradially outward from the support portion 13. A support portion may beformed by a plurality of teeth 22, which may be substantiallyrectangular in shape, elongated radially, whose periphery is circular,and crenellations 23 of slightly trapezoidal shape. The reception coils20 may be electrically excited by the transmission coil 19 connected toan oscillating circuit. The transmission coil 19 may generate byinduction an electric signal in the reception coils 20. During therotation of the encoder 8, the windows and the full portions of theoperational portion 14 passing before the microcoils may produce avariation of the metal mass situated in front of each receptionmicrocoil 20. In the reception coils 20, this may result in a variationof the phase of the electric signal induced due to losses by eddycurrents. These variations of the electric signal emitted by the variousreception coils 20 and processed by the circuit 18 may be the basis ofthe generation of signals representative of the parameters of rotationof the encoder 8, such as the speed of rotation.

In some embodiments, a sensor with microcoils may allow the instrumentedantifriction bearing to deliver reliable information, even when magneticfields of high intensity are present. The encoder may be made of anelectrically conducting and magnetic metal material, such as steel, orelectrically conducting and nonmagnetic material, such as aluminum orcopper.

Reception microcoils 20 may operate in pairs to deliver a differentialsignal. The reception microcoils 20 of a pair may be angularly offset byan angle represented by β. An angular pitch of the windows isrepresented by φ. For the signal to be out of phase, one of these anglesmay not be a multiple of the other. This therefore gives β≠a*φ where ais any integer, the angle β usually being greater than φ. For examplethis could be β=(a+0.5)*φ or β=(a+0.25)*φ.

When an encoder passes in rotation before the sensor, thediscontinuities of material of the operational portion 14 may causeperiodic variations of the metal mass that is opposite the receptionmicrocoils 20. If there is metal material before each of the coils of apair of reception coils, the phase difference between the twodifferential coils may be zero. If there is metal material before atleast one of the two reception coils forming a pair and the metalmaterial is distributed differently before each coil, the losses due tothe eddy currents in the metal material may generate a phase differenceof the currents. This phase difference may then be processed andextracted adequately by the processing circuit 18, in order to obtaindesired information, such as angular speed, direction of rotation,position, etc.

In some embodiments, generation of an electronic signal may not dependon the level or the direction of a magnetic field sensed by themicrocoils, but on the modification of the currents induced by theexcitation coil 19 in the reception coils 20 in the presence of thevariations of the electrically conducting metal masses passing beforesaid microcoils. The signal may be therefore very insensitive toexternal magnetic fields, which makes the device according to theinvention extremely suitable for operating in an environment subjectedto strong magnetic fields such as electric motors. The reception coils20 may be distributed on the support 17 with a radial position andangular pitch suitable for cooperating with the operational portion 14of the encoder 8 and/or delivering the required signals. In anembodiment, the number of reception coils 20 may be increased in thecircumferential direction and/or several coils may be stacked in theaxial direction in order to obtain higher powered signals.

In some embodiments, since the microcoils and/or processing circuit 18may be extremely thin, the sensor 7 may have extremely small axialdimensions, which may allow integration into a sensor unit 10. Likewise,the encoder may be, due to its structure, thin axially and may be easilyintegrated into the space between the bearing tracks, such that theencoder does not affect the external dimensions of the instrumentedantifriction bearing.

FIGS. 5 and 6 depict and embodiment of an encoder 8 made with a printedcircuit technique. From a conventional printed circuit substrate coatedwith a thin metal layer, such as copper, a disk may be made includingmetallized sectors 8 a and nonmetallized sectors 8 b. The substrate maybe electrically nonconducting and the metallized sectors 8 a may beelectrically conducting.

A disk may be coupled (e.g., by appropriate means, such as fitmentand/or bonding) onto an axial portion 3 d the rotating track 3 of thebearing 1. The axial portion 3 d may be configured to be coupled to thedisk. This type of encoder wheel has little inertia, great axialcompactness, and the contours of the active portions may be made withgreat precision. The aggregate signal may be particularly weak.

FIG. 7 depicts in greater detail the electrical functions of anembodiment of the system. Reception coils 20 may be grouped in two pairsnumbered 24 and 25 and framed by dashed lines. For clarity of thedrawing, the pairs of reception coils 24 and 25 are shown outside theexciting transmission coil whereas in reality they are inside saidtransmission coil 19. The coils 19 and 20 may be coupled to theprocessing circuit 18. The processing circuit 18 may include anoscillator 26, whose output is connected to the transmission coil 19,and two phase demodulators 27 and 28 coupled to the output of each ofthe reception coils 20. In an embodiment, the circuit 18 may include twointerpolating comparators 29, 30, positioned at the output of the phasedemodulators 27 and 28. At the output, the processing circuit 18 maytransmit a digital signal representative of at least one parameter ofrotation of the antifriction bearing, such as speed, position, directionof rotation, acceleration, etc.

In some embodiments, an instrumented antifriction bearing may beproduced that can be easily integrated into a mechanical assembly due toits small bulk. The instrumented antifriction bearing may operate athigh temperatures, such as those existing in an electric motor, and/oroperate in an environment subjected to strong magnetic fields. Throughthese qualities, the instrumented antifriction bearing according to theinvention has worthwhile capabilities for use in a high powerasynchronous electric motor. The instrumented antifriction bearing mayfulfill both the mechanical function of a bearing and the electronicfunctions of detection necessary to control the motor.

In this patent, certain U.S. patents, U.S. patent applications, andother materials (e.g., articles) have been incorporated by reference.The text of such U.S. patents, U.S. patent applications, and othermaterials is, however, only incorporated by reference to the extent thatno conflict exists between such text and the other statements anddrawings set forth herein. In the event of such conflict, then any suchconflicting text in such incorporated by reference U.S. patents, U.S.patent applications, and other materials is specifically notincorporated by reference in this patent.

Further modifications and alternative embodiments of various aspects ofthe invention will be apparent to those skilled in the art in view ofthis description. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the general manner of carrying out the invention. It is to beunderstood that the forms of the invention shown and described hereinare to be taken as the presently preferred embodiments. Elements andmaterials may be substituted for those illustrated and described herein,parts and processes may be reversed, and certain features of theinvention may be utilized independently, all as would be apparent to oneskilled in the art after having the benefit of this description of theinvention. Changes may be made in the elements described herein withoutdeparting from the spirit and scope of the invention as described in thefollowing claims.

1. An instrumented antifriction bearing device comprising: a rotatingportion; a nonrotating portion; and an assembly configured to detectrotation parameters, wherein the assembly comprises: an encoder; asensor, wherein the sensor is integrated with the nonrotating portion,and wherein the sensor comprises: a sensor unit; at least one receptionmicrocoil and at least one transmission microcoil, each microcoil beinga substantially flat winding, wherein said microcoils are positioned ona support of a circuit that is coupled to the sensor unit of thenonrotating portion, and wherein said microcoils are configured to bepositioned axially opposite the encoder.
 2. The device of claim 1,further comprising a plurality of substantially radial coplanarreception microcoils.
 3. The device of claim 2, wherein said microcoilsare linked in pairs, and wherein the linking reception microcoils areconfigured to generate a differential signal.
 4. The device of claim 1,wherein the encoder comprises an encoder wheel, and wherein the encoderwheel comprises an active zone, and wherein the active zone comprises anelectrically conducting metal.
 5. The device of claim 1, wherein theencoder comprises an encoder wheel, and wherein the encoder wheelcomprises windows.
 6. The device of claim 1, wherein the encodercomprises a printed circuit, and wherein the printed circuit comprisesan annular substrate with metallized sectors and nonmetallized sectors.7. The device of claim 6, wherein the printed circuit is coupled to arotating track of the antifriction bearing.
 8. The device of claim 1,wherein a space is defined between two cylindrical races of theantifriction bearing and frontal surfaces delimiting said races andwherein at least one portion of the encoder is positioned in said spacebetween the antifriction bearing tracks.
 9. The device of claim 1,wherein a space is defined between two cylindrical races of theantifriction bearing and frontal surfaces delimiting said races andwherein the encoder is positioned outside said space.
 10. The device ofclaim 1, wherein the sensor unit is substantially annular.
 11. Thedevice of claim 1, wherein the sensor unit occupies an angular sector ofless than approximately
 360. 12. The device of claim 1, wherein theencoder comprises an encoder wheel, and wherein the encoder wheelcomprises teeth.
 13. The device of claim 1, wherein the encodercomprises a printed circuit, and wherein the printed circuit comprisesan annular substrate with metallized sectors and nonmetallized sectors.14. An electric motor comprising: a rotor; a stator; at least oneantifriction bearing, wherein an antifriction bearing is configured tosupport the rotor; and a sensor assembly comprising: an encoder; and asensor, integrated with the stator, wherein the sensor comprises: atleast one reception microcoil and at least one transmission microcoil,wherein each microcoil comprises an essentially flat winding, andwherein said microcoils are positioned on a support of a circuit coupledto the sensor such that said microcoils are positionable axiallyopposite the encoder.
 15. An instrumented antifriction bearing devicecomprising: a rotating portion; a nonrotating portion; and an assemblyconfigured to detect rotation parameters, wherein the assemblycomprises: an encoder; a sensor, wherein the sensor is integrated withthe nonrotating portion, and wherein the sensor comprises: at least onetransmission coil; at least one reception coil; and a data processingcircuit; wherein a transmission coil, a reception coil, and a dateprocessing circuit are positioned on a support; wherein a reception coilis a substantially flat microcoil winding and said reception coil isconfigured to be positioned axially opposite the encoder.
 16. The deviceof claim 15, wherein the encoder comprises an encoder wheel, and whereinthe encoder wheel comprises an active zone, and wherein the active zonecomprises an electrically conducting metal.
 17. The device of claim 15,wherein the encoder comprises an encoder wheel, and wherein the encoderwheel comprises windows.
 18. The device of claim 15, wherein the encodercomprises an encoder wheel, and wherein the encoder wheel comprisesteeth.